swap: restore support for nofail

systemd stops adding automatic dependencies on swap.target to swap
units. If a dependency is required, it has to be added by unit
configuration. fstab-generator did that already, except that now it is
modified to create a Requires or Wants type dependency, depending on
whether nofail is specified in /etc/fstab. This makes .swap units
obey the nofail/noauto options more or less the same as .mount units.

Documentation is extended to clarify that, and to make
systemd.mount(5) and system.swap(5) more similar. The gist is not
changed, because current behaviour actually matches existing
documentation.

https://bugs.freedesktop.org/show_bug.cgi?id=86488

1 files changed, 34 insertions, 6 deletions

diff --git a/man/systemd.swap.xml b/man/systemd.swap.xml
index 44c16e7bc..1155758e2 100644
--- a/man/systemd.swap.xml
+++ b/man/systemd.swap.xml
@@ -117,12 +117,40 @@
                 <filename>/etc/fstab</filename> and a unit file, the
                 configuration in the latter takes precedence.</para>
 
-                <para>Unless the <option>noauto</option> option is set
-                for them all swap units configured in
-                <filename>/etc/fstab</filename> are also added as
-                requirements to <filename>swap.target</filename>, so
-                that they are waited for and activated during
-                boot.</para>
+                <para>When reading <filename>/etc/fstab</filename> a
+                few special options are understood by systemd which
+                influence how dependencies are created for swap
+                units.</para>
+
+                <variablelist class='fstab-options'>
+                  <varlistentry>
+                    <term><option>noauto</option></term>
+                    <term><option>auto</option></term>
+
+                    <listitem><para>With <option>noauto</option> the
+                    swap unit will not be added as a dependency for
+                    <filename>swap.target</filename>. This means that
+                    it will not be activated automatically during
+                    boot, unless it is pulled in by some other
+                    unit. Option <option>auto</option> has the
+                    opposite meaning and is the default.</para>
+                    </listitem>
+                  </varlistentry>
+
+                  <varlistentry>
+                    <term><option>nofail</option></term>
+                    <term><option>fail</option></term>
+
+                    <listitem><para>With <option>nofail</option> the
+                    swap unit will be only wanted, not required by
+                    <filename>swap.target</filename>. This means that
+                    the boot will continue even if this swap device is
+                    not activated successfully. Option
+                    <option>fail</option> has the opposite meaning and
+                    is the default.</para>
+                    </listitem>
+                  </varlistentry>
+                </variablelist>
         </refsect1>
 
         <refsect1>